MYST is one of those games that sticks with you no matter how much time has passed. While I prefer Riven, Myst laid the groundwork for the puzzle game genre for years to come. Every puzzle is intuitive and every little step of progress feels like you're doing something important. Uncovering the "mystery" of Myst is basically the foundation for what this kind of game should be.
While I love and have fond memories of Myst, nothing beats Riven on pure immersion alone. The game world is beautiful, beyond imagination, and feels so real despite being a game released in 1997 with a pixel count less than 1k. The fact that they were able to do all this and still have it be an even better puzzle game than Myst is truly a feat of design excellence. Myst was fantastic. Riven is unforgettable.